Fatigue in rheumatoid arthritis reflects pain, not disease activity.

OBJECTIVE: We determined the amount of fatigue experienced by patients with RA, and its relationship to synovitis, pain and other common clinical features. We also examined to what extent RA fatigue is improved by disease-modifying antirheumatic drugs (DMARDs) and anti-tumour necrosis factor (TNF) therapy.
METHODS: We studied two cohorts of 238 and 274 RA patients cross-sectionally and examined treatment responses in 30 RA patients starting anti-TNF and 54 starting DMARDs followed for 3 and 6 months. We measured fatigue using visual analogue scores (VAS) and Medical Outcomes Study Short Form 36 (SF-36) vitality scores. We recorded the disease activity score for 28 joints and its components (tender/swollen joint counts, patient global assessment, ESR), morning stiffness, health assessment questionnaire, physician global assessment, erosive disease, nodules, rheumatoid factor, concomitant medications and illnesses, and the SF-36 questionnaire.
RESULTS: Fatigue was common in RA patients; over 80% had clinically relevant fatigue (VAS > or =20 mm), over 50% had high levels (VAS > or =50 mm). It was associated with pain and changes in mental health, particularly depression. In each of the two cross-sectional cohorts, this relationship was similar whichever measures of fatigue and mental health were used. Fatigue fell with DMARDs and anti-TNF: before treatment, 87% of patients had high fatigue, after treatment this fell to 50%. These treatment effects were mainly linked to improvements in pain.
CONCLUSIONS: High fatigue levels characterize RA and are mainly linked to pain and depression. The association with disease activity is secondary. Fatigue falls with DMARD and anti-TNF therapy. The balance of evidence suggests that fatigue is centrally mediated in established RA.